Arching mechanism

ABSTRACT

Arching mechanism, for instance for backrests of seats, medical or orthopaedic apparatus or casings and the like, with a pressure element wherein at least one traction element connected with a tensioning mechanism engages, which, when the mechanism is actuated can produce bulging by preserving a relative elevation of apex of the convexity; the arching mechanism can comprise a frame with inserted pressure elements actuatable by adjusting device(s), whereby frame segments are length-variable pressure elements; traction elements provided with tensioning mechanism can engage a slitted, overlapping or bellows-like bulging body for the opening and closing of these areas, which produces a curving of the bulging body in a predetermined direction or directions.

This is a divisional of U.S. patent application Ser. No. 08/488,117,filed Jun. 7, 1995, now U.S. Pat. No. 5,626,390 which is a divisionalapplication of U.S. patent application Ser. No. 08/352,374 filed Dec. 8,1994 now U.S. Pat. No. 5,498,063 which is a divisional application ofU.S. patent application Ser. No. 07/820,870 filed Jan. 17, 1992 now U.S.Pat. No. 5,397,164 which is a national phase of PCT/AT90/00078 filedAug. 6, 1990 and based, in turn, upon Austrian application A1882/89filed Aug. 4, 1989 and A2133/89 filed Sep. 12, 1989 under theInternational Convention.

The invention relates to an arching mechanism, particularly for abackrest for a vehicle seat or seats for office and home furniture,respectively seats of all kind, as well as for use particularly inmedical or orthopaedic devices and apparatus, such as corsets or archsupports, in scaffoldings or casings, for the production of hulls, etc.

When for instance the arching of a backrest is adjusted, usually theapex of its convexity wanders according to the construction type of thearching mechanism over the height of the backrest, always remaining thesame. It does not adjust sufficiently to the constantly changingcurvature of a more or less curved spinal column, or to a stretching ofthe spinal column which is medically recommended or desired by the user.In constructions with shell seats, usually the lateral supportdiminishes with increased arching.

The EU-B-37656 shows a restraining frame for a motor vehicle seat,wherein a support piece is suspended by springs. The support piececonsists of two lateral parts connected to the frame by springs andmutually connected by cross elements. There is a centrally locatedadjusting shaft which can be actuated by a hand wheel, the shaft runningthrough so-called engagement devices, which in turn are connected to theoutermost points of the lateral parts via flexible connection elements.When the hand wheel is turned, an arching of the support part issupposed to result, whereby basically in the beginning only an expansionof the springs occurs. This type of construction affords support to onlya few vertebrae; the vertebrae lying above and below do not get the samestrong support. A freely suspended insertion of the support part in thebackrest or a construction wherein the support is suspended in theupholstery is not possible.

The DE-OS 2804703 shows a backrest wherein a plate having strapsarranged oppositely to each other can be arched via mutually engagedguide rails. The entire plate is height-adjustable by means of a rockerlever.

The EU-A1-322535 shows a backrest with an upper and a lower supportstrap which are interconnected by a vertical, flexible strap and aspring tensioned between them, whereby an adjusting shaft engages via agear in the lower support strap, in order to achieve an arching of thebackrest by bending the flexible strap.

Further, backrests made of foam material are known, which are supposedto adjust to the shape of the spinal column.

Another example is shown by DE-OS 3440846 which discloses an automobileseat whose backrest comprises a frame and a plate received in the frame.The plate is provided with vertically extending longitudinal slits inwhich a lumbar-support device is movable. The lumbar support can beadjusted by a hand wheel through a shaft linked onto the frame to varyits stiffness and to move it vertically.

The lumbar support is directly connected with the frame. As a result,all vibrations imparted by the road to the vehicle are fully transmittedto the back of the driver.

The known mechanisms do not permit any accommodation to changed orchanging curvatures of the spinal column. For instance, during long cartrips, the curvature of the spinal column alters greatly as a result ofthe required holding work, when the total weight of the upper body mustbe supported based on this disadvantageous position (hand stretched outtowards the steering wheel). This muscle work, respectively holding workin order to keep the body upright under conditions of improper orinsufficient support has to be performed entirely by the musculature andthe skeletal system, and thus logically leads to considerableexhaustion, as well as muscle stress. The involved muscles require forthis work up to 40 times more blood, respectively 40 times more energy,compared to an anatomically supported upper body (whose muscles do nothave to perform any holding work).

The support, respectively holding work must be performed by the archingmechanism and namely for all spinal columns (whose curvatures are asvaried as human faces--and which in addition, are constantly alteredfrom hour to hour due to tiredness, exertion and the required holdingwork--the height of a person decreases from morning to evening beapproximately 2 to 4 cm, and the spinal curvature changes in this timeperiod by up to 10 cm). Thus, an optimal arching mechanism has to act ina differentiated manner so that for instance when used in a backrest, itcan suitably support any shape of back, i.e. at least threefold and withvariable strength, as follows: 1. very strongly and stably in forwarddirection in the pelvic area (against the backward tilting of thepelvis), 2. somewhat gentler but equally firm radially and vertically inorder to support each vertebra in the lower-back (lordosis) area and 3.essentially stronger and vertically in an upward direction in thepectoral area under the shoulders against the weight of the upper body.

The additional support for the neck area can be a further requirement.

Once the arch is set and adjusted to the shape of the spinal column, itis naturally not allowed to change its shape even under fully exertedpressure, in order to insure full support independently from themomentary curvature of the spinal column of the user.

The at least triple support required from an ergonomically optimalbackrest can not be offered at all or only insufficiently by the knowndevices.

It is therefore the object of the present invention to avoid theabove-mentioned drawbacks and to create an ergonomically curvable andheight-adjustable arching mechanism with a wide spectrum of applicationand which, when used as a lordosis support insures a multiple, at leasta triple support.

The object of the invention is attained due to the fact that in itsupper and/or lower region, a general pressure element engages at leastone traction element connected with a tension element or a pressuremechanism, and that when the tension device or the pressure mechanism isactuated, the curvature caused by the mechanism occurs so that the apexof its convexity is maintained or is displaced with respect to itsrelative elevation.

The relative position of the apex of convexity is thereby consideredeither with reference to the used frame, or a seat or even the apex ofthe lordosis of the person, i.e. when the person moves in the seatthereby altering the lordosis, the apex of the convexity of themechanism has still to remain always adjusted to the lordosis.

Another embodiment of the invention comprises a frame and thereininserted pressure elements actuatable by at least one adjustment device,preferably pressure strips or surfaces, and the vertically runningsegments of the frame are length-variable over at least one adjustmentdevice.

In a further embodiment variant of the invention, the arching mechanismcomprises an arching body, which is slitted, overlapping or shaped likebellows and at least at these points traction elements provided with oneor several tension mechanisms engage for closing, respectively openingof these areas, whereby a curving of the arching body in each desired,preestablished direction can be achieved.

Further features of the invention can be understood from the dependentclaims, the specification and the attached drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages will become morereadily apparent from the following description, reference being made tothe accompanying drawings in which:

FIG. 1 is an elevational view of an arching mechanism according to oneembodiment of the invention;

FIG. 2a is an elevational view of another mechanism for this purpose;

FIG. 2b is a side elevational view of the mechanism for FIG. 2a butshowing a bulging thereof in broken line;

FIG. 3 is a side elevational view of the mechanism for FIG. 1 showingthe bulging thereof in broken line;

FIG. 4 is a view similar to FIG. 2a of still another mechanism accordingto the invention;

FIG. 5 is a side elevational view of the mechanism of FIG. 4 showing thebulged state in broken line;

FIG. 6 is a view of still another embodiment of the invention similar toFIG. 4;

FIGS. 6a, 6b are fragmentary elevational views showing anotherarrangement of the cable of the embodiment otherwise shown in FIG. 6;

FIG. 7 is an elevational view of yet another embodiment of theinvention;

FIG. 7' is an end view of the embodiment of FIG. 7;

FIG. 7" is a side view of this embodiment;

FIGS. 8',8" are elevational views of yet a further embodiment of theinvention;

FIG. 8a elevational view, partly broken away of an embodiment similar toFIG. 8', showing a different handle arrangement;

FIG. 8b is a side view of the embodiment of FIG. 8a, a bulging or bowedconfiguration being represented in broken lines;

FIG. 8c is a view similar to FIG. 8a with a slight modification of thestructure thereof;

FIG. 8c' is a side view of FIG. 8c with the bowed state being shown inbroken lines;

FIG. 9 is an elevational view of a frame structure for a furtherembodiment of the invention;

FIGS. 9a to 9e are used showing other actuating systems for the bowingof the device of FIG. 9;

FIG. 10 is an elevational view of yet another embodiment utilizing aneccentric drive for the bowing mechanism;

FIG. 10' is an end view of the embodiment of FIG. 10;

FIG. 10" side view of the embodiment of FIG. 10;

FIG. 11 is an elevational view of still another embodiment of theinvention, also using an eccentric to control the bowing of the frame;

FIG. 11' an end view of the embodiment of FIG. 11;

FIG. 11" is a side view of the embodiment of FIG. 11;

FIG. 12a a side elevational view of yet a further embodiment showing thebowed stated in broken line;

FIG. 12b is an elevational view of the embodiment of FIG. 12a;

FIG. 13 is a detail of one eccentric arrangement for effecting thebowing;

FIG. 14 is an elevational view representing a detail of anothereccentric arrangement according to the invention;

FIG. 15 is a perspective view illustrating the bowing of another archingdevice according to the invention;

FIGS.16, 16' are elevational views illustrating still another embodimentof the invention;

FIGS. 17, 17a are elevational views of yet a further embodiment of theinvention;

FIG. 17' is an end view of this latter embodiment;

FIG. 17" is a side view of the embodiment of FIG. 17;

FIG. 17'" is a detail view of the connection of the cable or the deviceof FIGS. 17 and 17";

FIG. 17"" is a detail view of another cable connection;

FIG. 18 is an elevational view diagrammatically illustrating a segmentalinstruction of the pressure elements which can be used in theembodiments previously described or subsequently described;

FIG. 19 is a diagram illustrating the principle of the inventionutilized in effecting bowing of various embodiments;

FIGS. 20, 20a are elevational views, partly broken away, of themechanism for applying tension to a cable as used in the invention;

FIG. 21 is a elevational view of yet another embodiment of theinvention;

FIG. 22 is a section taken along the line AA of FIG. 21;

FIG. 23 is an elevational view of yet another mechanism for effectingbowing of an arching mechanism according to the invention; and

FIGS. 24, 24a are views similar to FIG. 21 but illustrating yet anotherembodiment.

FIG.1, two vertically running and mutually spaced apart pressure rods 1,1' are connected by transverse ribs 13, 13', running perpendicularlythereto. The upper end of the row of transverse ribs forms an end stripor slide strip 14, the lower end is formed by a support plate for thepelvic edge. The end strip 14, as well as the support plate 8 isprovided on its outer edges with bores, wherein springs 16, 16' aresuspended, which again engage in a frame of the backrest, not shown inthe drawing. In between and parallelly to the two pressure rods 1, l'starting from the end strip 14 down to the middle area of the archingmechanism, runs a locking or traction-assisting strap 9 in whose upperregion a rod-like traction element 2, e.g. for instance a bicycle spoke,is suspended. A' is the upper application point of the traction force. Afurther traction element 2' is suspended in the support plate 8 at B,which forms the lower application point of the traction force. The twotraction elements 2, 2' are further connected with a tension lock 3,arranged in the central area of the arching mechanism, which can beactuated via a hand wheel fastened to the end of a shaft protruding fromthe arching mechanism.

When the hand wheel is turned, the mechanism starts to bulge, since bothtraction elements (2, 2') are pulled together.

FIG. 3 shows the path (h) between X1 and X2 travelled by the apex theconvexity not dislocated from its original plane, during the arching ofthe mechanism.

In the embodiment of FIG. 2, the tension device is a bowden wire 10,whereby the traction element is a wire running in a sleeve. The upperand lower application points of the tension device on the arching bodyare again marked A' and B'.

In the embodiment according to FIG. 4, the tension device is also abowden wire 10. The traction element 2" slidable within its sleeve bymeans of a screw drive, respectively a worm gearing 22, 23, is a wire,respectively a bowden wire, engaging at the right side of the supportplate 8. In the area where the wire exits the sleeve, the latter isconnected with a further traction element. This traction element is arod 2'", which is linked to the right-side area of a lever 7, whichagain is connected via a short traction element with thelocking-assisting strap. From the left edge of the lever 7, a tractionrod leads to the left area of the support plate 8. Due to thisconstruction of the tension device, it is again possible to achieve abulging of the entire mechanism by keeping the apex of the convexity inplace, since at the actuation of the wire line, the traction rod runningoutside on the left is entrained.

The embodiment shown in FIG. 6 is essentially based on the one shown inFIG. 4, but between the lever 7 and the end strip also a traction spring4 is provided and in the extension of this spring, between the lever 7and the support plate 8 a compression spring 5 is provided, wherebybetween the compression spring 5 and the support plate 8 a tighteningset screw 6 is provided.

The function of the lever can be taken over by a guide groove providedin the support plate 8, whereby the traction element designed as a wirecoming from the sleeve of the bowden wire runs over the groove, isredirected and runs up to the end strip, where it has a fixed end (FIG.6).

Corresponding to FIG. 4, from the point where the wire exits the sleeve10, a traction rod runs parallelly thereto.

FIG. 7 is an embodiment of the arching mechanism, wherein the pressurerods 1' are located at the extreme outer edge of the construction,forming the vertical segments of a frame. The support plate for thepelvic edge is connected via a traction rod with a lever which in turn,starting from its two ends, is connected on the one hand with a firsttraction-assisting strap and on the other hand, with the sleeve of thetraction wire of a bowden wire, whereby the cable engages in a secondtraction-assisting strap which is mirror-inverted to the first, withrespect to the center line of the construction.

FIG. 8 shows an embodiment of the arching mechanism with two parallel,vertical pressure rods, with transverse ribs arranged perpendicularlythereto and with a traction-assisting strap in the vertical median axisof the construction. On this traction-assisting strap, a tractionelement 2'" is arranged, which is connected with a tension lock 3actuatable by a hand wheel. The outmost areas of the arching mechanismare connected to two traction springs 4, 4, which are located outside ofthe pressure rods and parallelly thereto. The parts shown in brokenlines show the position of the construction after a bulging. Instead ofthe tension lock 3', the actuation can also take place over a lockingeccenter 17, 17' (FIG. 8c, 8c').

According to another concept of the invention, the arching mechanismcomprises a frame whose vertical crossbars form the pressure elements.The frame is horizontally subdivided in two parts. As shown in FIGS. 9,9a, 9b, 9c, 9d, 9e, the mutually spaced-apart frame ends are eachconnected with a lever arm, whereby the respectively neighboring leversare interconnected and linked to traction elements. Furthermore, theends forming the open areas in the frame are each provided with a sleeveon each side of the frame.

As shown in FIG. 9a, each two neighboring levers are centrally connectedeach other, whereby each time the lower lever is connected via atraction element with the upper crossbar of the frame and the two upperlevers have a connection with the lower crossbar, wherein an adjustingdevice not shown in the drawing is interposed as an intermediary link.

When this adjusting device is actuated, the traction elements archprimarily the bulge at the outer edges of a for instance shell-shapedbackrest, whereby the pressure elements are subjected to an extension.Instead of pressure rods, it is also possible to use pressure surfaces.

This way, primarily an active bulge of the shell rim is created, wherebyinwardly arching transverse ribs (wires, straps, nets) are activelyarched in the area wherein also an arching of the shell is supposed totake place, due to the fact that they are entrained on their part, in afixed or springy manner, together with the two (or several) activearching edges of the shell. The shell shape of a surface remainsunimpaired by the intensity of the arching; the shell shape can even beemphasized. For instance, the bulging of a seating surface can beincreased, without thereby decreasing the depth of the shell.

FIG. 10a, b, show a construction wherein the levers engaging at the endsof the divided frame can also lead to an actuation device via a tractionelement. This arrangement comprises a disk plate centered on thevertical centerline of the construction, which can be rotated by meansof a handle. The handle can be fixed in notches (FIG. 10b). The diskplate has two almost circular, decentered, mutually offset recesses,each of them having one traction element leading to the lower area andone traction element leading to the upper area of the frame, this wayforming a double eccenter. FIGS. 10' and 10" show the shape of theconstruction after the bulging process. The device for bulging theconstruction described in FIG. 10 finds use also in FIG. 11, howeverhere it is centrally inserted in the arching mechanism, whereby fromeach one recess of the eccenter two traction elements extend to theouter reaches of the frame, symmetrically to the vertical centerline.

The shape achieved after the actuation of the arching device is shown inFIG. 11".

The FIGS. 13 and 14 show for instance accenter disk actuatable via acable line or a rack-and-pinion combination, whereby the disk itself isdesigned as a toothed wheel.

FIGS. 12a, b show a lever connected to the lower support plate via aspring, which lever is in turn connected via traction elements with theupper, respectively lower regions of the arching mechanism and can befixed in notches after the corresponding bulging of the backrest(represented in broken lines).

FIG. 15 shows a combined construction, wherein the height as well as thebulge can be simply adjusted, whereby the traction elements marked "W"are responsible for the bulging and the traction elements marked "HV"are responsible for the height adjustment.

FIG. 16 shows an embodiment of the arching mechanism basically identicalto the one of FIG. 1, wherein however during bulging the entiremechanism slides along two rods symmetrically arranged with respect tothe vertical median axis.

The arching mechanism shown in FIGS. 1 to 24 can have further pressureelements (rods, surfaces, gratings, etc), which can be bulged indifferent directions, by providing for instance in one or several pointsinterruptions (open portions, overlappings) or locking straps or areassimilar to bellows (FIG. 18).

During traction, the traction elements used in such constructions, whicheither traverse the pressure elements or bypass them (possibly withinterposed spacers), due to the tension of one or several tensionmechanisms close the open, respectively overlapping interstices,respectively areas designed like bellows in the pressure elements, insteps or continuously. When using locking straps or other suitablemeans, the reinforced areas are in any case subject to either reduced orintensified bulging. Due to this aforementioned partial or completeclosing of the open portions or folds, a bulging occurs with respect tothe areas of the pressure elements which are not interrupted or designedlike bellows also in the direction transverse to the traction elements.Traditionally, a bulging surface can be arched only approximatelyparallelly to or in the direction of the pressure element(s). Due tothis "multidimensionally" bulging construction, it is possible to obtaineven spherical or the like surfaces by closing the opposite open ends ofa flat or slightly curved surface.

Such a construction type can be of use for instance in construction forcasing elements or in naval construction. The surface to be bulged, forinstance, can already be curved in advance by spring force and can bethen made to bulge in the same or in the opposite direction, by slightlyactuating the tension device. As a tension device for the archingmechanism according to the invention, it is possible to use also asimple cable winch, coil or bobbin, which can also serve for largerlength changes in the traction, respectively pressure elements.

It is also possible to use several arching mechanisms, whereby theireffects can be compounded or annihilate each other, so that for instanceone or several additional bulges in an already existing bulge can beachieved.

In this type of construction it is possible that--no matter which of thecooperating arching mechanisms are individually involved and in whichway--when the main traction element is relaxed all the individualarching units arranged to work together, against each other oroverlappingly, as well as the entire arching mechanism can be set tozero or to an intermediate or extreme value, and that when anotherarching process is started, only that part of the arching mechanismparticipates in the bulging, which according to the set slits, controllevers, eccenters, etc and their lost motion areas (slits or other freespaces of the traction or pressure elements or of their articulations,stops, etc) are supposed to be actively arched (e.g. FIG. 19).

In the embodiment of the arching mechanism represented in this figure,it is possible to obtain any shape, from a minimal to a maximal bulge,depending on the position of the lever H (in broken lines or in stronglyextended position). Depending on the positioning of the lever H alongthe line IHV provided with direction arrows, an internal displacement ofthe apex of the convexity can take place (positions S1, S2, S3).

FIG. 20 shows a similar embodiment, wherein the variable archingpossibility of the arching mechanism and the internal height adjustmentoccur via a bowden wire, linear motor and modular system.

The arching mechanisms mentioned in the specification or also individualelements thereof can be manufactured in a construction assembly,respectively modular system and can be quickly assembled, replaced,repaired, and varied, respectively combined with any heretofore-known orfuture components or construction elements by using adequate connectionelements, e.g. elements like bicycle spokes with heads insertable incorrespondingly shaped bayonet-type fittings or the like or other plug,clip or clamp connections, etc. This modular construction type makespossible an individualized production of the mechanism, since allelements of the invention are selectively interchangeable with oneanother or can be integrated with already existing foreign elements(e.g. when the mechanism is built into an already existing seat oranother construction element). The arching mechanisms according to theinvention can replace the heretofore-used arching mechanisms or can bearranged in addition to the latter in selected angular positions orparallelly in any desired combination.

The arching can be performed mechanically, electrically, pneumatically,and so on, directly or by remote control, and namely so that the apex ofconvexity can be height-adjusted at will or can be produced within theconstruction at will.

FIG. 21 shows an embodiment wherein the arching mechanism has beenintegrated in a backrest.

The backrest consists for instance of a U-shaped downwardly open frame27 and a frame crosstie 28. Inside this U-shaped frame, there are twovertically running tension wires 29, fastened to the frame. As shown inFIG. 21, these tension wires can be shaped for instance meander-like intheir upper portion. Also in the upper portion of the tension wires, afurther tension wire 29' runs horizontally through the backrest. In thelower portion of the two tension wires 29, which is basicallyrectilinear (but can also be offset to accommodate the gearing), a firstgearing 30 is provided, which can be mounted by means of clamp elements31. The first gearing 30 has a worm, a wormwheel and a pinion (all notshown in the drawing) connected to displace the first toothed rack 32.The toothed rack 32 is traversed in its lower area by a transverse shaft33. The gearing has a high transmission ratio, and thus the adjustmentof the support can be effected with small forces and low torque. Thepressure element is received by the tension wires 29, which also serveas slide wires, i.e. the pressure element is slidably arranged thereon.

The general pressure element is advantageously composed of an upper endstrip 34, mutually spaced-apart transverse ribs 35, 36, 37 and a supportplate 38 preferably arranged in the lower area of the backrest for thesupport of the pelvic edge of the spinal column, in this order. Theseelements are connected by at least two pressure strips 39 which areparallel to the tension wires. The upper end strip and the support plateare each slidably arranged on the tension wires by means of two slideeyes 40, 40' and 41, 41'.

The first gearing 30 is connected via a flexible shaft 42 with anelectromotor 43, arranged for instance in the lower area of thebackrest. When the first gearing 30 is actuated, a height adjustment ofthe general pressure element takes place. On the upper end strip 34, asecond gearing 44 is arranged, which equivalently to the first gearing30, is in working connection with a second toothed rack 45 via a hightransmission rate. This gearing is also driven by an electromotor 43'via a flexible shaft 42'. This second gearing is rigidly mounted to theupper area of the general pressure element Preferably, the two gearingare of identical construction and due to the reduced forces involved canbe made of plastic material. Preferably, the two gearings fastened byclamp elements 31 to the tension wires 29 can be simply mounted ordismounted. The two gearings are preferably made of plastic material,molded material, diecast metal or sheet metal.

The general pressure element does not necessarily have to be built inthe manner described above, for instance it can be made of one orseveral bulging plates of any pressure-resistant but flexible material,which again can be closed, perforated or grid-like or with a thicknessand resistance which varies in certain portions thereof, in order tomake possible the formation of different or identical curvatures indifferent areas.

In this embodiment, a triangular rocker lever 47 is articulated to thesecond toothed rack 45 by a pivot pin 46. The rocker lever has twobores, for instance one in its center and the other one in its endremote from the pivot pin. The left bore of the rocker lever shown inPig. 21 is connected via rigid spoke 48 with the upper end strip 34 andover a further spoke 49 with the support plate 38.

When the second toothed rack is actuated, a curving of the pressureelement occurs, since the distance between the support plate and theupper end strip has to change, but the spokes remain rigid. Depending onthe curvature, the apex thereof wanders upwardly or downwardly. Theposition of the rocker lever (from slightly upwardly inclined toslightly downwardly inclined) depends on the selected degree of bulgingof the support. Depending on the placement of the intermediate bore ofthe rocker lever, differing transmission ratios can be created. Bymodifying the length of the second toothed rack, the fulcrum formed bythe pivot pin is entrained. If the distance of the bores is equally big,the spoke will complete only half the stroke compared to the secondtoothed rack (halved force equals double stroke).

Since the arching mechanism slides along the tension wires by means offour eyes, which can also be replaced by slide rings, it has provenparticularly advantageous to use snap elements for this purpose, forinstance open, especially U-shaped elements which narrow down towardsthe opening.

This way, the entire construction can be treated as a module and can bereplaced or mounted in seconds, during mounting or necessary repairs.The motors 43, 43' are advantageously mounted on the frame by means offastening brackets 50.

All or some of the individual elements "under tension" of theconstruction are kept at a distance with respect to the general pressureelement (or parts thereof) either for instance by the offset ends (51,52) of the general pressure element, as can be seen from FIG. 22 whichis a section along the line A--A in FIG. 21, or by separate spacingelements, respectively construction elements, or by a slightprestressing of the traction elements, etc., which determines thedirection of bulging. Further, an embodiment with a common drive is alsoconceivable.

A general representation of this variant can be found in FIG. 23.

A further embodiment, similar to the one shown in FIG. 21 is shown inFIG. 24. The drive of the arching mechanism takes place here over bowdenwires 53 and two linear motors 54, 54'. The linear motor 54 arranged inthe figure to the right serves for the direct, respectively indirectcontrol of the bulge.

A direct bulge control takes place then when the bowden wire engagesdirectly at the arching mechanism. The control shown in the drawingfigure which takes place via the transmission rocker lever 55 is anindirect control. This can also take place via guide rollers, curves,etc.

The control shown in the figure to the left represents a double-actinglinear drive 54', which on one side retracts the bowden control cable53' and on the opposite side relaxes the same cable. This way forinstance the height adjustment of the pressure element along the tensionor slide wires can be performed, but it can also be achieved on or inslide rails, in or on slide surfaces, in shell bodies or directly infree space, suspended on or hanging from one or several bowden wires.

The bowden-wire sleeve 56 guiding the bowden control cable 53' isattached on top and bottom to the guide wire by means of a suspendedeyelet spoke or directly to the frame (in points D, F, G). The movablebowden control cable or any other traction or control cable can now beclamped at selected points by means of one or several snap or screwconnections and fastened at a selected point (in this figure marked withthe possibilities A, B and C) via a control lever, or also over rods, ora cable winch, a thrust linkage, whereby at the displacement of the wireinside the bowden control wire or one of the aforementioned devices, thearching mechanism is synchronously moved together with the wiredisplacement. If the connection is made at the uppermost point (A) ofthe arching mechanism, during bulging, due to the shortening of theentire bulging surface, the apex of the convexity also wanders upwardlyexactly with the same percentage corresponding to the relation of thelengths between the upper edge and the apex, as well as the lower edgeand the apex.

First of all, this can be very important from the medical point of view,since in the base of a bulging for the "small-of-the-back archedposition" the person is also somewhat stretched.

If the fastening is done at the apex, the apex of convexity remainsconstant for instance with respect to the seat. In the case of aconnection at the lowermost point of the mechanism (C), during bulgingthe total length reduction resulting from arching becomes effective onlyat the uppermost end of the arching mechanism, and all other points, aswell as the apex of convexity are displaced downwardly, incorrespondence only to a percentage relation of the various length ofthe individual halves of the arching mechanism.

Naturally, the apex of convexity remains here unchanged, considered withrespect to the person, since the person becomes somewhat shorter whenthe spinal column is bent (the last mentioned embodiment suits thiscase) and the lordosis sinks thereby slightly downwardly.

Thus, each way of fastening depends primarily on the fact whether it isintended to synchronize the motion with the person. In an active backsupport, the apex of the convexity must be fixed. Then, the person canfind full support in the heightwise resting apex, when getting shorterdue to the arched back position. This way, the arching mechanism and notthe spinal column bears the weight of the upper body.

Further, it is conceivable to have a trailing or a forerunning phaseshift between the fixed apex of the lordosis and the apex of the archingmechanism, i.e. an overcompensation, respectively undercompensation ofthe apex takes place.

It is self-understood that the arching mechanism can be used in additionto other constructions or integrated in such constructions (for instanceattaching the mechanism to an already existing backrest). Further, itshould also be pointed out that the mechanism or elements thereof can bein connection with a memory, whereby bulging and apex position can beprogrammed and can be brought automatically in the selected positionwith the use of chips, magnetic cards, keys, etc. or the desired(required) bulge height, respectively apex point displacement can be setmechanically, e.g. with the aid of a four-way switch (tumbler).

As a result of this embodiment of the arching mechanism, wherein thecontrol unit is clamped with the bowden control wire and it is possibleto select at will the application point of this unit on the mechanism,preexisting conditions of the edges, such as hard or soft upholstery,various desired suspensions of the mechanism in a preexisting frame,etc. can be simply taken into consideration in any desired way, withoutjeopardizing the operation of the arching mechanism.

It is not only possible to over- or undercompensate the movements, butalso to take into consideration the respective seat constructions,upholstery materials, covers, suspensions, and so on.

The arching mechanism of the invention, described above with referenceto backrests, can of course be applied to many other fields, such asmedical or sports apparatus, toys, life-saving equipment, for variousprotective and carrying constructions, and so on.

We claim:
 1. A lumbar support for a back of a seat, comprising:aflexible structure having an upper portion and a lower portion, saidflexible structure adapted to bow upon displacement of said upper andlower portions toward one another, thereby forming a curvature having anapex; a traction mechanism for drawing said upper and lower portionstoward one another, said traction mechanism including a first verticalrod attached to said upper portion and a second vertical rod attached tosaid lower portion, and an adjustment member for moving said first andsecond vertical rods in an upward or downward direction; and whereinsaid first vertical rod is attached to a midsection of said upperportion and said second vertical rod is attached to a midsection of saidlower portion of said flexible structure.
 2. The lumbar supportaccording to claim 1, further comprising a handwheel for operating saidtraction mechanism.
 3. The lumbar support according to claim 2, whereinsaid handwheel is connected to a shaft which drives said adjustmentmember.
 4. The lumber support according to claim 1, wherein uppermostand lowermost portions of said flexible structure are movably supported.5. A lumbar support for a back of a seat, comprising:a flexiblestructure having an uppermost portion and a lowermost portion, saidflexible structure adapted to bow upon displacement of said uppermostand lowermost portions toward one another; a traction mechanism fordrawing said uppermost and lowermost portions toward one another, saidtraction mechanism including a first vertical rod attached to an upperportion of said flexible structure and a second vertical rod attached toa lower portion of said flexible structure, and an adjustment member formoving said first and second vertical rods in an upward or downwarddirection; and wherein said first vertical rod is attached to amidsection of said upper portion and said second vertical rod isattached to a midsection of said lower portion of said flexiblestructure.
 6. The lumbar support according to claim 5, furthercomprising a handwheel for operating said traction mechanism.
 7. Thelumbar support according to claim 6, wherein said handwheel is connectedto a shaft which drives said adjustment member.